1. Field of the Invention
The present invention relates to a component of a turbomachine of a composite material comprising a ceramic matrix and a corrosion protection layer arranged on the component, as well as to a method for producing such a component of a turbomachine.
2. Discussion of Background Information
Composite ceramics comprising a ceramic matrix, into which in particular ceramic fibers are incorporated, i.e. so-called CMC (Ceramic Matrix Composite) materials are advantageous materials for components of turbomachines, for instance of static gas turbines or aircraft engines, since they are substantially resistant to aggressive ambient conditions and high temperatures, and furthermore have high strength values even at high temperatures.
Such fiber-reinforced ceramics are usually formed from aluminum oxide, silicon carbide, carbon or mullite, in which case the incorporated fibers may be formed from the same materials. In particular, the fibers and the matrix may have an identical or similar chemical composition, for example carbons reinforced with carbon fibers, silicon carbides reinforced with silicon carbide fibers, or aluminum oxides reinforced with aluminum oxide fibers. Mixtures, however, are also possible, for example silicon carbides reinforced with carbon fibers.
Although in many cases these materials already have a sufficient high-temperature stability in atmospheres containing oxygen, under certain ambient conditions, for example in atmospheres containing steam, damage to the material may occur, when, for example in the case of composite ceramics comprising silicon carbide, volatile silicon hydroxide compounds are formed in the presence of steam.
For this reason it is necessary to protect the above-described composite ceramics against aggressive atmospheres and corrosive media by a corrosion protection layer.
From the prior art, it is already known to provide protective layers based on barium-strontium aluminosilicates (BSAS) or based on silicates of rare earths (RE) (RE-SiO5 or RE-Si2O7). However, protective layers based on these materials have the disadvantage that they are inclined to glass phases which do not form sufficient protection, and with these layers the problem also arises that they may form volatile silicon hydroxide compounds in the presence of steam.
In view of the foregoing, it would be advantageous to have available a component for a turbomachine of a composite ceramic comprising a corrosion protection layer arranged on the composite ceramic, as well as a corresponding method for its production, with which the disadvantages of the prior art are reduced or avoided, and in particular the corresponding component is insensitive to aggressive atmospheres and corrosive media, the intention being in particular to provide protection against degradation by atmospheres containing steam. Furthermore, the component should be producible simply and reproducibly, as well as reliably usable.